Air samplers

ABSTRACT

With reference to FIG.  1,  and air sampler  1  for use in analysing biological or other analytes, comprises an airflow chamber  2  having an air inlet  3  and an air outlet  4.  An extract from  5,  draws ambient air in through the inlet  3,  and then through the chamber  2,  to discharge it back to atmosphere by way of an outlet  6.  The airflow chamber  2  houses a cyclone air/liquid separator  7  through which the inflowing air is caused to pass. An injector  8  introduces liquid into air flowing through the air inlet  3.  The cyclone separator  7  extracts this liquid and any entrained particles therein and discharges it from the airflow chamber  2,  initially by way of a duct  9,  where it is then conveyed to a collection vessel  12,  by way of a three channel peristaltic pump  13,  and a duct  14.  The collection vessel  12  is housed within a Peltier-cooled holder  15  to maintain the contents of the vessel  12  within the 2° C.-8° C. range which is desirable for maintaining the integrity of biological analytes such as bacteria or proteins. Analyses such as PCR, culture on agar plates or immunoassays may be performed on the collected samples. The holder  15  also houses sample bottles  16, 17, 18  and  19.

[0001] This invention relates to air samplers and particularly, but notexclusively, relates to air samplers for sampling the ambientatmosphere, in order to detect and measure contamination that may bepresent.

[0002] The present invention provides an air sampler for collectingcumulative samples from large volumes of air in small volumes of liquid,(e.g. particles from 100 cubic metres of air in about 10 mls of liquid).

[0003] In addition sequential samples may be taken automatically. Thesesamples may be kept cool to preserve them for later analysis.

[0004] According to the present invention, an air sampler comprises anair flow chamber having an air inlet and an air outlet, means forintroducing liquid into air flowing through the chamber so as to entrainany particles present in the airflow, means for collecting theentraining liquid and any entrained particles therein, and fordepositing the same in a collection vessel, means for returningcollected entraining liquid to the airflow chamber, means for detectingthe presence of bubbles in the returning liquid, and operable tointroduce fresh entraining liquid into air flowing through the airflowchamber, and means for collecting a sample of the entraining liquid andany particles therein, which may be present in said collection vessel.

[0005] An embodiment of the invention will now be described by way ofexample only, with reference to the accompanying drawings wherein:

[0006]FIG. 1 is a diagrammatic illustration of the air sampler, and

[0007]FIG. 2 is an enlarged detail of part of FIG. 1.

[0008] With reference to FIG. 1, an air sampler 1 for use in analysingbiological analytes, comprises an airflow chamber 2 having an air inlet3 and an air outlet 4.

[0009] An air mover 5, conveniently an extraction fan, draws ambient airat 500 to 1000 litres per minute in through the inlet 3, and thenthrough the chamber 2, to discharge it back to atmosphere by way of anoutlet 6.

[0010] The air flow chamber 2 houses a cyclone air/liquid separator 7through which the inflowing air is caused to pass.

[0011] Means comprising an injector 8 introduces liquid into air flowingthrough the air inlet 3. The cyclone separator 7 extracts this liquidand any entrained particles therein and discharges it from the airflowchamber 2, initially by way of a duct 9, where it is then conveyed to acollection vessel 12, by way of one channel of a single three channelperistaltic pump 13 and a duct 14. The collection vessel 12 is housedwithin a Peltier-cooled holder 15 to maintain the contents of the vessel12 within the 2° C.-8° C. range which is desirable for maintaining theintegrity of biological analytes such as bacteria or proteins. Analysessuch as PCR, (Polymerase Chain Reaction), culture or agar plates orimmunoassays may be performed on the collected samples.

[0012] The holder 15 also houses bottles 16,17,18 and 19.

[0013] A large pore (e.g. 25 micron) filter unit 25 is fitted in theduct 9 to remove large particulates present in the collected air whichare unsuitable for a particular assay. Diesel soot, for example. Thefilter unit 25 will, however, allow soluble enalytes or smallparticulate analytes, such as bacteria and viruses, to pass through.

[0014] The sampler 1 further comprises recirculation means for returningcollected entraining liquid from the vessel 12 to the airflow chamber 2where it is discharged to air flowing into the cyclone 7. These meanscomprise an extraction line 30, a bubble detector 31, a pinch valve 32,and a discharge line 33 which passes through another of the threechannels of pump 13. The bubble detector 31 is connected to electroniccircuitry, which includes, a programmable timer 34, by way of anelectronic signal line 35. The circuitry incorporates a controllingmicroprocessor.

[0015] A reservoir 36 houses entrainment liquid 37, comprisingde-ionised water containing 0.01% of a non-ionic detergent such asTween-20 and 10 mM HEPES N-2-hydroxyethyl piperazine-N¹-2 ethanesulphonic acid buffer; pH 7.5. Line 33 draws this liquid from thereservoir 36 by way of the pinch valve 32, and passes it, via aneedle-gauge stainless tube, which forms the injector 8, into the airflow inlet 3, at about 2.0 millilitres per minute.

[0016] Aerosol particles entrained into the liquid stream exit from theair flow chamber 2, (via a standard Luer-fitting port), and through pump13, to be deposited in the collection vessel 12.

[0017] The collection fluid is re-circulated from the vessel 12 backinto the airflow chamber 2 by way of line 30, bubble detector 31, pinchvalve 32, pump 13 and line 33. This continues until the level of liquidwithin the vessel 12 falls to a point whereby air rather than liquid isdrawn into line 30. When the entrained air reached the bubble detector31, an electronic signal is sent via line 35 to the microprocessor inthe electronic circuitry which includes programmable timer 34. Themicroprocessor then operates the pinch valve 32, so that, for a pre-setperiod of time, fresh collection fluid is drawn from the reservoir 36and discharged into the airflow chamber 2, by way of line 33, pinchvalve 32, pump 13, line 33 and injector 8.

[0018] After the set period the pinch valve 32 is operated so that thesystem is restored to the re-circulation mode, which continues until theliquid level falls again in vessel 12, and air is again entrained.

[0019] A time delay is built into the system so as to allow fluid fromthe re-charged vessel 12 to reach the bubble detector 31.

[0020] In addition, a start up routine is programmed into timer 34 toallow initial charging of the system.

[0021] As mentioned above, pump 13 is a single three channel pump. Twoof the channels of the pump are used for pumping liquid into and out ofthe airflow chamber 2. The remaining channel is used to draw off smallvolumes of liquid for discharge to a selected one or more of the samplebottles 16, 17, 18 and 19, via line 39 and three-way valves 40, 41 and42. (See FIG. 2).

[0022] In this example, the flow rate of entraining liquid into theairflow chamber 2 and cyclone 7 is ca.2 millilitres per minute, thesample for analysis may be drawn off at a much lower rate of ca.50microlitres per minute, using smaller bore tubing. This allows anintegrated sample of aerosol particles to be collected for up to 8 hoursinto a standard 25 ml “universal” bottle. In the present embodimentthere are four sample bottles, (16-19) so monitoring the air for an8-hour working shift, or a full 24 hour day, is possible without theneed for an operator to be present. In addition, the programmable timer34 allows the equipment to be positioned and then to be activatedautomatically at set times up to one week in advance. For 4 samples, the3-way valves (40-42) are needed to direct the sample flow.

[0023] The collected samples are subsequently analysed in theconventional manner.

1. An air sampler comprising an airflow chamber having an air inlet andan air outlet, means for introducing liquid into air flowing through thechamber so as to entrain any particles present in the airflow, means forcollecting the entraining liquid and any entrained particles therein,and for depositing the same in a collection vessel, means for returningcollected entraining liquid to the airflow chamber, means for detectingthe presence of bubbles in the returning liquid, and operable tointroduce fresh entraining liquid into air flowing through the airflowchamber, and means for collecting a sample of the entraining liquid andany particles therein, which may be present in said collection vessel.2. An air sampler as claimed in claim 1, provided with programmabletimer means operable to obtain air samples at pre-determined times. 3.An air sampler as claimed in claim 2, incorporating a microprocessor forcontrolling the sampler.
 4. An air sampler as claimed in claim 1, 2 or3, wherein said fresh entraining liquid is introduced when the level inthe collection vessel falls to a level whereby air is entrained in thereturned collected liquid, and is detected by the said means fordetecting bubbles.
 5. An air sampler as claimed is any one of claims 1to 4, provided with a plurality of sampler bottles and means fordrawing-off liquid so as to divert it to the bottles.
 6. An air sampleras claimed in any one of claims 1 to 5, provided with a three channelpump and a plurality of sample bottles, wherein two of the channels ofthe pump are used for pumping liquid into and out of the airflowchambers and the third channel is used to draw-off liquid and divert itto a selected sample bottle.
 7. An air sampler as claimed in claim 6,wherein the pumps is a single, three channel peristaltic pump.
 8. An airsampler, substantially as herein before described, with reference to theaccompanying drawings.